The Matra-BAe AIM-132
Advanced
Short Range Air Air Missile (ASRAAM) was selected during the late 1990s
as the RAAF's new Within Visual Range (WVR) AAM, and is
planned
for use on the F/A-18A+, and possibly other RAAF types. This capable
missile is currently deploying to UK RAF squadrons, providing a quantum
leap in capability over the established AIM-9 Lima all aspect missile.

The RAAF's AIR 5400 requirement stemmed from a major in
regional capabilities, with the PLA-AF to deploy in excess of 350
potent
long ranging Sukhoi Flanker variants (300+ Su-27PK/SK and up to 60 or
more Su-30MKK), and the InAF deploying 50 Su-30MKIs (including the
would
be TNI-AU buy), armed with the very effective Vympel R-73M/AA-11 Archer
WVR AAM and late models of the Vympel R-27/AA-10 Alamo BVR AAM.
Malaysia
is at this time negotiating for the Su-30MK.

It is expected that most Flanker users will also acquire the
newer R-77/AA-12 Adder BVR AAM, regarded to be a Russian equivalent to
the US AIM-120A AMRAAM, as well as the R-74 digital variant of the R-73
series. The RAAF will in turn acquire the current build AIM-120B AMRAAM
to fulfill the BVR missile requirement in AIR 5400, replacing the now
obsolescent AIM-7M Sparrow semi-active homing AAM. The RAAF committed
in
1998 to stretch the Hornet with a view to introducing its replacement
in
the 2010-2015 timescale. The aircraft will be fitted with new
countermeasures, slightly faster AYK-14 mission computers, JTIDS, and
the APG-73 RUG II AI radar, a development of the APG-65 radar family
used on the F/A-18C/D and F/A-18E/F.

The RAAF's new WVR AAM is required to outperform the Archer,
with superior kinematics and a better high off-boresight capability,
using a Helmet Mounted Display (HMD). The ASRAAM, the Rafael Python 4
and the AIM-9X were competitively evaluated, with the ASRAAM selected
over the other two contenders. The AIM-9X is a fundamental redesign of
the AIM-9, retaining only the existing 4.5 in motor, warhead and fuse,
and using a new Focal Plane Array seeker and thrust vectoring tail
control section. The Israeli Python 4 is a unique missile, discussed in
an earlier issue of Air Power International. The advanced but arguably
immature German Bodensee-Geratetechnik Iris T was not evaluated. The
Iris T combines large aerodynamic strakes and thrust vectoring, and
recent reports suggest the incorporation of a Focal Plane Array seeker
to replace the previous scanned seeker.

The Su-27/30 is of particular concern since it
aerodynamically
outclasses the F/A-18A+ in virtually every category, and challenges the
Hornet in the area where it has traditionally excelled, which is tight
low speed manoeuvring. Therefore the selection of the ASRAAM provides a
capability intended to offset this advantage.

The AIM-132 ASRAAM - An
Historical Perspective

The ASRAAM is a revolutionary rather than evolutionary step
in
AAM design, as it embodies a range of new technologies and a design
philosophy which is both new and unique in this class of missiles.

Historically, the origins of the ASRAAM date back to the
eighties, when a Memorandum of Understanding (MoU) was signed between a
primarily European group and the Americans over the future of AAM
designs for NATO aircraft. The MoU divided responsibility for the next
generation missiles along the division of the new WVR missile to the
Europeans, and the radar guided Beyond Visual Range (BVR) missile to
the
US. The BVR missile solidified into the AIM-120 AMRAAM, which despite a
protracted development process, has become a superb in service weapon.

The "European" consortium comprised four nations which split
the share of development costs. The four players were the UK (42.5%),
Germany (42.5%) and Norway (5%), with Canada (10%) which was the only
odd player in the group.

The intent of the arrangement was for the US to supply the
AMRAAM, and the Europeans to supply the ASRAAM, at preferential prices.
In this fashion the Europeans sought to capitalise on their past
experience designing heatseeking missiles, and the US on their
experience with BVR missiles. Since the US had at that time designed
and
manufactured the AIM-7 Sparrow and AIM-54 Phoenix, and the Germans
developed the then potent ALASCA and jointly with the Norwegians, the
Viper, the division made very good sense both technically and
politically.

The early ASRAAM definition envisaged a missile shorter, and
fatter than the established Sidewinder, which used inertial midcourse
guidance and an advanced Infra-Red seeker for terminal homing. To
accommodate the then wide range of launch rails in service, the ASRAAM
was to use an adaptor, termed a Missile Support Unit, which would
remain
on the rail after launch. BAe Dynamics and Bodensee Geratetechnik (BGT)
formed a joint company, named BBG, for this purpose. Definition of the
missile design began in 1984.

As is often the case with complex multilateral arrangements,
the ASRAAM began to slowly unravel. By February, 1988, US unhappiness
with the direction of the project led to a series of intended design
changes. The weakening position of the USSR, and Europe's strengthening
economic position both significantly reduced US interest in the
program.
By February, 1989, the missile was ready to enter the full scale
development phase, but the program was already dying a political death.
Germany pulled out in July, 1989, thereby killing the multinational
ASRAAM project off entirely.

ASRAAM trial launch at the
USAF Eglin test range (USAF).

The UK was not happy with this situation, by any means. The
Soviet deployment of the Su-27 equipped the AA-11 Archer seriously
challenged the unmanoeuvrable Tornado ADV, and clearly the new
Eurofighter would need a high performance missile to be effective. The
RAF has always taken the air combat manoeuvring game seriously, and the
prospect of a world full of Flankers and Fulcrums shooting some very
good missiles was a capability which would have to be balanced, at the
least.

Clearly the collapsed AIM-132 ASRAAM project provided a good
starting point for a UK national WVR AAM development project. As a
go-it-alone UK effort, it was no longer necessary to make either
operational or technical compromises, to satisfy the pork-barrelling
needs of other players. This meant that the "new" ASRAAM could be built
to what the RAF regarded to be its optimal operational specification,
and the choice of optimal components to meet such a spec could be made.
By August, 1989, the ball was rolling, and BAe invited bids from
subcontractors. In October, the Hughes SBRC (Santa Barbara Research
Centre) Focal Plane Array Indium Antimonide imaging device was selected
for the missile's seeker.

By 1990, with the collapse of Warsaw Pact, defence budgets
began to rapidly contract in the West, and the UK MoD subsequently
competed the BAe ASRAAM design against a joint GEC-Marconi and Matra
bid
with the heatseeking MICASRAAM missile, and a German BGT bid.
Evaluation
of the bids continued until early 1992, when the UK MoD announced that
the BAe bid had been selected, and a USD 912 million contract was
awarded for development, production and supply of the ASRAAM missile
for
the RAF. Full Scale Development commenced in March, 1992, and the UK
MoD awarded an additional contract for missile supply in May, 1994.

The missile is expected to be operationally deployed at some
time in the latter half of next year. It will be carried by the new
Eurofighter, the Tornado ADV and IDS, the Harrier GR.7, the Sea
Harrier,
the Jaguar and if required, the Hawk combat capable trainer.

The AIM-132 ASRAAM - A
Technical Perspective

The ASRAAM is radically different in many respects from other
established and development missiles designed for WVR combat. The
missile is heavily optimised for best possible pre-merge performance,
following the contemporary dictum that whoever gets the first shot off
is likely to win. Therefore the missile is built from the outset to
acquire an opponent and successfully engage it at maximum range. Should
the first shot not succeed, the missile is designed to provide close-in
performance to destroy the target aircraft at close quarters.

The key to the missile's acquisition range performance and
high off-boresight capability is the 128 x 128 element Focal Plane
Array
seeker. The Hughes SBRC device is manufactured as a single
Indium-Antimonide die, and is in effect a single chip low resolution
thermal imager sensitive in the 0.5 to 5.4 micron band. The device is
typically cooled to 80 Kelvin using a Hymatic Joule-Thompson Argon,
Nitrogen or air driven gas expansion refrigerator fed from an onboard
bottle or launcher umbilical. The FPA is mounted on a two axis gimbal
which provides full forward hemisphere coverage.

FPA devices of this ilk provide revolutionary capabilities in
comparison with traditional rotating reticle seekers. First and
foremost, the FPA dramatically increases sensitivity, because it
"stares" continuously at the target thus exposing a much larger
detector
area for much longer to the target's emissions. Moreover, because it
uses a television style scan, rather than conical reticle scan, it is
for all practical purposes immune to flares as well as blinking
infrared
jammers. The only robust countermeasure is a laser with sufficient
power
to blind it or burn it out.

F/A-18A
wingtip
station carrying an ASRAAM (C. Kopp)

Because the FPA produces in effect a TV picture of the target
scene, it is virtually impossible to break lock by violent manoeuvre at
any range, moreso since the gimbal mechanism will adjust the line of
sight of the FPA. The target airframe is tracked using contrast lock
techniques similar in concept to those used by the Maverick ASM, and
therefore escape from seeker coverage is geometrically impossible
providing the airframe can keep up.

The FPA seeker is mounted in the nosecone, under an optical
filter dome, together with the cooling assembly and support electronics.

Aft of the seeker section is the electronics, fusing and
warhead section. The electronics section contains the DASA built
inertial package, which is an ASRAAM specific 3-axis solid state
accelerometer/fibre optical gyro package with sufficient navigational
accuracy to fly the missile blind into the acquisition basket, where
the
seeker acquires the target. This is indeed conceptually the same model
as is used by radar guided missiles such as the AMRAAM.

The electronics section also contains the video signal
processing electronics which analyse the picture produced by the FPA
seeker, these are implemented in Application Specific Integrated
Circuits (ASIC), ie custom Silicon implementing algorithms developed by
BAe Dynamics. A flight control processing package runs software which
manages the missile state, implements the navigation and autopilot
algorithms, and the modified proportional navigation homing algorithm.
The BAe Dynamics custom designed processing package uses an array of
800
series Transputer chips, and is regarded to be the most computationally
powerful ever fitted to a missile. The software is written in US DoD
standard ADA language, a high level macro language is employed to
automatically generate source code for compilation.

The missile can be fired in both Lock-On Before Launch (LOBL)
mode as a conventional heatseeker, or in Lock-On-After-Launch (LOAL)
mode, in a manner more akin to a BVR radar guided weapon. The missile
can also be used as an expendable Infra-Red Search and Track unit.

The missile has two umbilical interfaces, providing both a
digital and analogue interface, and compatibility with Sidewinder and
AMRAAM umbilicals. Support is provided for aircraft electrical power,
and a thermal battery is used for inflight power supply. The interfaces
allow the missile to be cued by a Helmet Mounted Sight or Display
(HMS/HMD) or by aircraft radar, and a Sidewinder tone is produced for
the pilot's headset.

In UK service, the missile will be cued by the new Pilkington
Optronics HMD, currently in development for the new EF 2000 Eurofighter
Typhoon. The Eurofighter avionic system includes the PIRATE IRS&T
system, which will also have the capability to cue the ASRAAM to a
target, enabling a totally passive (ie radar silent) engagement.

The Pilkington Optronics HMD will have the capability to
project raster video from the PIRATE IRS&T on to the visor, and
will
include NVG style image intensifier tubes embedded in the helmet, thus
providing a true night vision capability covering the pilot's whole
field of view (FOV).

The ASRAAM warhead is a compact DASA built blast
fragmentation
design, fired by a Thorn-EMI laser proximity fuse, which is a
conventional approach for a Western WVR missile. A backup impact fuse
is
employed. Since the ASRAAM achieves high accuracy, it is in effect a
"hittile" and therefore arguably the warhead serves the purpose of
guaranteeing the otherwise almost certain kill produced by a hit with a
high velocity missile airframe.

The missile's REMUS powerplant is unique in several respects.
Manufactured by Royal Ordnance, Summerfield, the motor uses a
proprietary strip steel laminate casing, rather than a conventional
machined tubular casing. The laminated casing is stiffer, lighter, and
much more tolerant of physical mishandling or shrapnel/spall/bullet
damage in comparison with conventional designs. The casing forms a
combustion chamber which exhausts through a blast tube and fixed
geometry nozzle. With a 6.5" external diameter, the motor contains
roughly 70% more propellant per unit length in comparison with the
established Mk.36 Sidewinder motor. Using a low smoke, low flame
propellant, the motor is designed with a boost only burn profile. As a
result, the missile exhibits arguably the best kinematic performance of
any contemporary WVR missile design.

The missile is controlled by a high torque servo package
driving four independent tail surfaces. The Lucas Aerospace actuator
package is wrapped around the exhaust blast tube.

The ASRAAM airframe is aerodynamically very clean, designed
for minimal drag at high speeds. The only geometrically compromising
features are the three Sidewinder standard launch rail lugs.

Performance and
Operational Philosophy

The ASRAAM is designed to enable the early engagement of
opposing fighter aircraft, and this is reflected in the missile's
combination of highly sensitive FPA seeker, midcourse inertial package
and high energy motor. In a pre-merge engagement scenario, the FPA
seeker allows target acquisition at significant BVR ranges, and the
inertial midcourse guidance package means that the missile can be fired
if necessary even blind to intercept an inbound threat aircraft. The
high energy motor provides very high acceleration, and range
performance
which has traditionally been the domain of radar guided BVR missiles.
Like its BVR active radar counterpart, the AMRAAM, ASRAAM will fly
itself to a geometrically appropriate position, activate its seeker,
acquire the target and home to impact. Because a short burn motor is
used, and the FPA seeker is of course passive, the victim aircraft may
have little if any warning of the inbound ASRAAM.

The reflects the RAF's current air combat doctrine which
regards the bomber threat as the primary objective of an air defence
fighter. Therefore the ASRAAM is built to enable a defending fighter to
break up opposing fighter escorts in the premerge, to provide the
defending fighter with an early opportunity to engage the escorted
bomber package. The ASRAAM can be fired in multiple round rippled salvo
launches.

While the premerge optimisation of the ASRAAM design is
perhaps its most remarkable design feature, the missile is also
designed
to be highly effective in close combat. It achieves this by using its
high off-boresight capability, inertial midcourse capability, and high
acceleration. The ASRAAM can be fired at very high G loading / Angle of
Attack (AoA), cued by a Helmet Mounted Sight, at targets within the
pilot's entire field of view.

This means that the missile can be fired "over-the-shoulder"
to engage a threat in the beam or aft sector of the launch aircraft,
providing that the pilot can sight the target. Because midcourse
inertial guidance is used, the target need not be in the seeker's field
of view at launch. This is a design feature which is at this time
unique
to the ASRAAM.

As a result, the ASRAAM is a particularly attractive
defensive
missile for a bomber, as it can fire at a pursuing fighter even at an
appreciable range. This capability significantly complicates life for
fighters attempting to engage an ASRAAM equipped bomber. A Helmet
Mounted Display will be required for the bomber. It will be interesting
to see whether the RAAF opts to so equip its 35 strong fleet of
F/RF-111C and F-111G aircraft. While an avionic upgrade for the F-111G
has been approved in principle, the specific configuration of the
upgrade is still being worked on. Fitting the F-111 fleet for the
ASRAAM
would provide a respectable air defence capability (with 6 rounds) with
the ability to effectively engage hostile LRMP, reconnaissance and
transport aircraft at extended ranges, while making the F-111 a much
less inviting target for hostile fighters. The digital AMRAAM
compatible
interface will be required to fully exploit the missile.

It is worth noting that over-the-shoulder launching is a
fundamentally different approach to that taken by the Russians, who
have
addressed this problem by producing a rearward firing variant of the
R-73 Archer, the R-73R, which uses an additional booster to overcome
the
aircraft's forward velocity. The rearward firing Archer is cued by the
Flanker's NIIP N-O12 tail warning radar.

In comparison with its contemporaries, the AA-11 Archer, the
Rafael Python 4, the BGT Iris T and the AIM-9X, the ASRAAM is
fundamentally different in both design philosophy and intended mode of
operation. Its extended range performance provides a unique BVR
capability, which in effect overlaps the capabilities of radar guided
BVR missiles. Its combination of heatseeking and inertial midcourse
guidance provides it with a much larger engagement envelope in close
combat.

In turn, its different design philosophy will by default
impose a quite different air combat manoeuvring model, one which is
designed to exploit the missile's uniquely different characteristics.

It is thus very difficult to make meaningful comparisons
between the ASRAAM and its rivals, on the basis of trivial performance
specs alone. The ultimate metric of effectiveness with any missile
design is its achieved kill ratio in live combat. This kill ratio is a
function of missile capability, launch aircraft capability, air combat
doctrine and the pilot's ability to exploit all three to best
advantage.
The adoption of the ASRAAM will require that the RAAF 81 WG evolve a
new
package of ACM tactics and doctrinal model, to best exploit this
weapon's unique capabilities.

It is without any doubt that the adoption of the AIM-132
ASRAAM and AIM-120B AMRAAM will provide the RAAF's now increasingly
obsolescent F/A-18A with a potent improvement in BVR and WVR
capability,
over the now clearly obsolete AIM-7M Semi-Active Homing Sparrow and the
AIM-9M reticle seeker equipped Sidewinder. While this will address the
near term shortfall in capability, in the longer term a new fighter
will
be required as regional Flanker deployments build up to their currently
expected number of more than 400 airframes. The ADF's AIR 6000 program,
which starts in earnest in 2000, will identify the eventual
replacements
for the F/A-18A and F-111.